Foodstuffs on a tray cart are frozen solid by being stored in an insulated compartment and there exposed to an immediate heat exchange which takes place with a cryogenic refrigerant that is to be introduced. The refrigerant is usually liquid nitrogen or liquid carbon dioxide. This refrigerant is sprayed into the insulated compartment by means of a spraying system, where it develops a gaseous constitution upon contact with the foodstuffs which are to be supercooled, or, frozen. The cold refrigerant, which from this point is gaseous, is circulated by one or more fans, penetrates over and over again the various shelves of the storage cart. Finally, it is drawn off from the insulated compartment through an exhaust. It is unavoidable that the food provisions that are positioned closer to the spraying system are cooled more intensively than those farther away. Because of the irregular and uneven exposure to introduction of the refrigerant gas, there is consequently a variation in the refrigeration and freezing conditions where individual products are concerned. This situation is especially undesirable in the case of perishable foodstuffs.